This invention relates to a braided electric fence rope for use in fences, or as the fence itself, to contain livestock within an enclosure, and to keep unwanted animals out of an enclosure or from crossing the fence or other barrier.
Traditional fences are barrier type fences which attempt to keep animals in or out of the enclosure by creating an immovable barrier. Stone walls and wood were the early materials of choice. Barbed wire and high tensile wire have been widely used for many years. Vinyl board fence and wire mesh fence are more recent developments. Recycled rubber, rigid pipe, polymer coated wire and extruded polymer (non-metallic) wire are all used today as fence materials.
Fences have always presented problems. They are expensive to build and troublesome to maintain. When a weak link is found, or created, by an animal, or by a falling tree, the fence is penetrated. When a fence is penetrated, animals escape from the enclosure with the risk of serious injury to animals or people, and potential loss of the animals.
Animals, particularly horses, can both damage and be damaged by traditional fence materials. Horses can kick through wood fences, chew wood until it is severed, get puncture wounds from wood splinters, nails and loose wire ends, get cut by wire, and get serious injuries from loose ends of wire which tangle around their legs.
The most frustrating problems to farmers are the time, trouble and cost to erect traditional fences, and the constant need to repair them.
Electric fence technology introduced a psychological deterrent to fences. An animal does not like to receive an electric shock. Electric fences are used as additional deterrents to supplement and protect traditional fences made of wood or wire or plastic.
Several attempts have been made to devise a strong and durable electric fence, suitable for use as a permanent fence. Electrified high tensile wire on posts has been widely used as permanent electric fencing, but it has several disadvantages. Wire is heavy and cumbersome to install and repair. Wire expands as the temperature increases requiring tightening, then contracts with reduced temperature which creates tensional strain and leads to breakage. In addition, wire is inelastic and can be snapped by a sharply applied force. Wire is hard for animals to see against woods and typical farm backgrounds, it rusts, and can cut animals and cause puncture wounds.
Another type of electric fence rope is made by twisting wire conductors with strands of fibreglass or polymer fibres to form a twisted rope. The disadvantage is that twisted rope tends to xe2x80x9cunlayxe2x80x9d under tension and to elongate. The fence rope must then be retightened, which restores tension but causes the rope to unlay further. The wire is generally lightweight and inclined to break under tension, particularly when the fibre stretches and the wire does not. Increasing the size of the wire conductor increases the weight and the cost of the fence rope. Substituting a high strength metal wire, such as stainless steel, for a low strength conductive wire, such as copper, reduces the electrical conductivity of the fence line, because the stainless steel is much less conductive than copper.
A further type of electric fence line comprises tapes woven from a plurality of textile or fibreglass threads with electrically conductive filaments of wire woven-in longitudinally, as disclosed by Olsson in U.S. Pat. No. 4,449,733. Such wire could tend to break under tension.
An electric fence line is disclosed by Monopoli in U.S. Pat. No. 5,036,166. In reviewing the art, Monopoli stated that prior electric fences are encumbered with the major disadvantage that they employ relatively fragile electrical conductors of low tensile strength, which are also prone to work hardening and consequential breakage, particularly at points along the line where the line has been knotted or twisted, subjected to abrasion or to tensional forces in the line. The patent is directed to overcoming such problems by loosely incorporating highly conductive strands into the fence line and by incorporating an additional electrically conductive strand of high strength into the fence line in touching relationship with the highly conductive strands. Thus the fence has a highly electrically conductive metal strand, such as copper, with at least one high strength metal strand of lower conductivity, such as stainless steel. The metal strands are oriented in touching relation so that in the event of breakage of the highly conductive strand, the high strength metal strand will bridge the break with only a minimal increase in the total electrical resistance of the fence line.
Another type of electric fence rope, disclosed by Moore in U.S. Pat. No. 4,819,914, comprises an inner core of stranded wire conductor cable and an outer insulating layer of braided synthetic fibre elements that completely surround and physically isolate the conductor cable so that no conductive portion of the conductor cable is exposed. It is disclosed that even though these synthetic fibre elements insulate the cable, the fence rope will still provide an electric shock to an animal contacting these outer synthetic fibre elements. However, it is apparent that the shock could not be as effective as if the conductor was not insulated. Also, in practice, because the inner core cable is heavy and tiff, this fence rope is difficult to work with.
Similarly, Orser, in U.S. Pat. No. 3,805,667, has disclosed a braided rope in which an electrical conductor runs longitudinally within each strand comprised of a plurality of yarns, and each strand is enclosed within a tubular braided cover. The plurality of tubular braided strands are then plaited together, but the electrical conductor is not exposed.
Electric fence ropes developed in the form patented by Moore and Orser have the serious disadvantage that the conductive elements are buried within non-conductive elements which insulate the conductors from providing the maximum electrical shock to an animal contacting the rope. In consequence the electrical conductor is made larger and heavier to reduce its electrical resistance, as in Moore""s stranded wire cable, and the rope becomes inflexible and stiff to handle.
Composite electric fence lines are typically used only for portable and temporary fences within permanent fences because of the lightweight materials employed. Most electric fence line products on the market tend to break easily, and the package labels frequently warn that these types of fences must only be used within permanent fencing.
The best of traditional fence systems leave much to be desired. The demand for improved fencing is world wide, in a host of applications. Every domestic animal must be contained as cost effectively and safely as possible. Farmers need a stronger, more easily handled portable fence for rotational grazing. Farm crops and stored hay need more effective protection from animals, including deer and elk in some areas. Grazing animals must be kept back from the shores of lakes and rivers to reduce riverbank erosion. A solution needs to be found to the increasing number of highway traffic accidents caused by moose-vehicle and deer-vehicle collisions.
It is an object of an aspect of this invention to provide an improved electric fence rope with the inherent strength and resilience to not break under the normal applied forces from animals and other impacts, while providing an electrical shock to deter animals from contacting the fence.
Accordingly, an aspect of the present invention provides a braided rope for an electrical fence comprising an exterior layer of electrically conductive elements in the form of wires and non-conductive elements in the form of synthetic fibres, said electrically conductive elements and non-conductive elements being braided together to form the exterior layer such that the electrically conductive elements are in a helical configuration, said rope being electrically conductive between opposed ends thereof.
In a preferred embodiment, the exterior layer of the braided fence rope is constructed around an inner core of high strength non-conductive elements, such as polymer fibres.
Another aspect of the present invention provides an electrically conductive rope for an electric fence comprising a cylindrical tightly woven braided exterior layer, said braided exterior layer being formed from a plurality of elements, at least two of which are conductive elements and the remainder of which are non-conductive elements, each of said conductive elements being a plurality of electrically conductive wires and said conductive and non-conductive elements being braided to form said cylindrical tightly woven braided exterior layer such that the conductive elements are helically wound with opposed orientations, said conductive elements being on the surface of the exterior layer and being in electrical contact at periodic intervals along the exterior layer, said flexible rope optionally having an inner core of non-conductive synthetic fibres.
In a preferred embodiment of the present invention, the braided exterior layer is formed from 8-32 braided elements, preferably 16 braided elements, and especially where two of the braided elements are conductive elements.
In another embodiment, the fence rope has a breaking strength of at least 400 kg and an elongation at break of 15-20%.
In a further embodiment, the braiding of the fence rope is formed with a tightness of 4-32 pics/inch, especially 8 pics/inch.
In yet another embodiment, the fence rope is capable of being twisted, knotted, tied or bent.
In preferred embodiments, the conductive elements are a plurality of copper wires, especially 3-8 copper wires in each twisted strand, in which the copper wires are of a gauge of 20 or smaller, especially in the range of 20-40, most preferably 30 gauge, gauge being defined by the American Wire Gauge Standard. The copper wires are preferably twisted together into two or more strands.
In further preferred embodiments, the non-conductive elements are formed from fibres of polypropylene, polyamide or polyester.
In another embodiment, the fence rope does not undergo a change in length with changes in ambient temperature.
In a further embodiment, subjecting the fence rope to a load in tension of up to 200 kg and subsequently releasing such load does not cause an increase in the 30 length of the fence rope.
In other embodiments, the braid is a marine yacht braid as used for sail halyards and spinnaker sheets.